## Tuesday, March 19, 2013

### ANNA UNIVERSITY ME/MTECH 2013 EXAM MODEL MODERN DIGITAL COMMUNICATION TECHNIQUES JANUARY 2011

M.E./M.Tech. DEGREE EXAMINATION, JANUARY 2011.
First Semester
Computer and Communication
(Common to Communication Systems)
250101 — MODERN DIGITAL COMMUNICATION TECHNIQUES
(Regulation 2010)
Time : Three hours Maximum : 100 marks
PART A — (10 × 2 = 20 marks)
1. What is meant by coherent and non-coherent detection?
2. What are the advantages of MSK when compared to QPSK?
3. What are the disadvantages of multicarrier OFDM modulation system?
4. What is meant by guard time and cyclic extension in OFDM?
5. State Shannon’s channel coding theorem.
6. Define linear block code.
7. What is meant by systematic convolutional code?
8. What is meant by constraint length and free distance for convolutional code?
9. State Nyquist pulse shaping criterion for zero ISI.
10. What is meant by correlative coding?
Question Paper Code : 20098

PART B — (5 × 16 = 80 marks)

11. (a) (i) Explain the non-coherent detection of binary FSK signals with neat
block diagram. (9)
(ii) Explain about Gaussian MSK. (7)
Or
(b) Draw the block diagram of M-ary PSK transmitter and receiver and
explain in detail.
12. (a) Draw the block diagram of a multicarrier OFDM digital communication
system and explain function of each block in detail.
Or
(b) Explain in detail any two methods to reduce peak-to-average power ratio
in multicarrier OFDM system.
13. (a) (i) Explain orthogonal and bioorthogonal binary codes. (10)
(ii) Explain binary coded DPSK with infinite quantization. (6)
Or
(b) (i) Explain the error detecting and correcting capabilities of linear
block code. (6)
(ii) Write short notes on :
(1) BCH code and
(2) Read-Solomon Code. (5 + 5)
14. (a) A convolutional code is described by the following generator sequences :
(1 0 0) 1
g =
(1 0 1) 2
g =
(1 1 1) 3
g =
(i) Draw the encoder diagram for this code.
(ii) Draw the state and trellis diagrams for this code.
(iii) Find the code word corresponding to the message sequence 10101.
(4 + 8 + 4)
Or
(b) (i) Explain Viterbi decoding algorithm for convolutional code. (8)
(ii) Explain Turbo encoder with block diagram. (8)
15. (a) Explain duo-binary signalling scheme without and with precoder for
controlled ISI.
Or
(b) Draw the block diagram of adaptive linear equalization and explain with